Behavioral Components of Equine Gastric Ulcer Syndrome

Experts suggest undesirable behavior in horses may be due to chronic pain and underlying medical issues, most likely musculoskeletal conditions, equine gastric ulcer syndrome (EGUS), and dental disease.^*

What the Studies Say

Anecdotal reports suggest that aversive behavior occurs commonly in patients with EGUS. The scientific literature, however, is divided with some studies supporting this association and others refuting. For example, studies show that 25% of horses with squamous gastric disease had girthiness, and 31% of horses with glandular gastric disease had girthiness. Additionally, the studies report that about one-third of those horses also presented with changes in behavior. On the flip side, other studies failed to identify any real relationship between resolution of glandular lesions with resolution of owner-reported behavior changes.

“These findings have led some commentators to draw into question the relevance of EGUS as a differential diagnosis for the clinical presentation of aversive behavior,” wrote the experts of a recently published comprehensive review on this topic.

Looking further at girthiness in particular, one study reported that 13 of 37 horses presenting solely for girthiness underwent gastroscopy to directly visualize the stomach. Twelve of those 13 horses were ultimately diagnosed with EGUS, and the girthiness completely resolved in 10 horses after treating them with omeprazole.

This study provides the first direct evidence of a relationship between changes in aversive ridden behavior and EGUS, according to the researchers.

“Together, what this means is that EGUS should be considered when evaluating horses with aversive behavior,” said Ashley Fowler, Ph.D., a nutritionist for Kentucky Equine Research.

But it’s not the top of the list.

Differentials for Pain-Based Aversive Behavior

“According to Sykes and Lovett, if a horse’s sole aversive behavior occurs during riding or tacking up, musculoskeletal disease, including saddle fit, should be the primary suspect. The next top differential for pain-based aversive behavior is EGUS, and finally dental disease,” Fowler shared.

If the horse’s history includes changes in eating behavior or weight loss, then squamous gastric disease becomes more likely.

With this in mind, working up cases presenting for aversive behavior should begin with performing a basic musculoskeletal and lameness exam, followed by gastroscopy in a sedated horse, and a full oral exam while still sedated.

Sykes and Lovett further advised that a holistic approach should be taken when addressing pain-based aversive behaviors as some cases may have more than one disease; a combination of poor farriery, improper saddle fit, and unsound dentition could all be in play.

Treatment Options

When a horse is diagnosed with EGUS via gastroscopy, Sykes and Lovett first treat with omeprazole for squamous disease and a combination of omeprazole and sucralfate for horses with glandular disease or both squamous and glandular together. They closely assess response to treatment for seven days. If an improvement in the aversive behavior is noted, the full course of standard EGUS treatment is initiated.

“If no improvement in aversive behavior is identified following EGUS treatment, then Sykes and Lovett would consider other findings, such as musculoskeletal issues. They recommend treating horses with phenylbutazone or ‘bute’ for five to seven days and assess response to treatment,” Fowler said. “Further, any dental disease should also be corrected.”

Again, this approach addresses the fact that multiple concurrent disease processes could be present.

Don’t Be Fooled by Learned Behavior

When horses do not respond to treatment, Sykes and Lovett suggest considering that the “persistence of aversive behavior is a manifestation of a learned response.”

Girthiness, for example, could persist if the pain due to EGUS was longstanding and the aversive behavior is ingrained. Even partial response to treatment should be considered important in horses treated for EGUS.

If there is a learned behavior component, then behavioral modification is indicated as well as massage or playing specific types of music during tacking up for “creating positive associations during tacking.”

Managing EGUS

In addition to following vet recommendations for treating EGUS, there are some diet and management changes that may help manage this disease. These strategies are aimed at reducing the exposure of the stomach lining to low pH gastric fluid, either through buffering activity or physical barriers.

“For example, providing continuous access to forages helps in two ways. First, forage ingestion requires a lot of chewing. This stimulates saliva production, which helps buffer stomach acid. Additionally, forage also creates a fiber mat in the stomach that can act as a physical barrier between the stomach acid and the upper gastric tissue. This is why feeding forage before exercise is recommended to help reduce the risk of ulcers,” Fowler mentioned.

Further, adding an oil supplement, such as ReSolvin EQ, that contains the specific fatty acids EPA, DHA, and GLA reduces the incidence and severity of gastric ulcers in a research study conducted by Kentucky Equine Research.

^*Sykes, B., and Lovett A. 2025. Can all behavioral problems be blamed on equine gastric ulcer syndrome? Animals 15(3):306.